Designing Service APIs with AI Assistance
The contracts between your services are the most important design decision in a microservices architecture. Get them right, and teams can work independently. Get them wrong, and every change cascades across the entire system. This lesson covers contract-first API design using OpenAPI and gRPC, with AI tools accelerating the design and code generation process.
Watch: Video Walkthrough
Key Concepts
- Contract-First Design: Defining the API contract before writing implementation code
- OpenAPI Specification: Writing machine-readable REST API contracts
- gRPC and Protobuf: High-performance service-to-service communication with type safety
- AI Code Generation: Using Claude and Cursor to generate server stubs and client SDKs from contracts
Hands-On Exercise
Task: Design an OpenAPI 3.1 specification for an order management service with endpoints for creating, reading, updating, and canceling orders. Use Claude or Cursor to generate a Node.js Express server from the spec, then generate a Python client SDK from the same spec.
Pro Tips
When using AI to generate API contracts, provide real-world example payloads rather than abstract descriptions. “Generate an OpenAPI spec where an order has items, shipping address, and payment method — here’s an example JSON” produces far better results than “generate an order API.”